Electrical filter



Sept. 29,1931..

H. W. HOUCK ELECTEIGAIJV FILTER AFiled May 17, 1926 i v Y lNvENToR Har@ YY1/Jauch BY Qmwf M( ATTORNEY Patented Sept. 29, 1031 UNITED STATES v1,824,819V I A'PATENT OFFICE HARRY W. IHOUCK, OF MOUNT VERNON, NEW YORK, ASSIGNOR TO DUBILIER CON- DENSER CORPORATION, OF NEW YORK,

N. -Y., A CORPORATION OF DELAWARE ELECTRICAL FILTER Application led May 17,

This invention relates to electrical filters; particularly electrical filters for smoothing out-variations of electric current and rendering such current uniform in value.

An object of the invention is to provide a filter capable of obviating oscillations of radio frequency in electric circuits connected,

`for example, to a radio receiving set.

The nature and scope of the invention will be madeclear in the following description, taken with the accompanying drawings, and the novel features thereof pointed out in the appended claims. But the disclosure is, of course, intended to be illustrative only, and I may vary the details of the arrangements herein set forth to a considerable extent and still keep within the -principle bywhich the invention is controlled.

On the drawings Figures 1, 2 and 3 vindicate diagrammatically several embodiments of a filter according to my invention, all operating in much the same manner. i

The same numerals identify the same parts throughout.

In apparatus Afor utilizing current taken from the light or power circuit of the house or building, to operate radio receiving sets in place of dry batteries heretofore used to energize the anode or plate circuit or the filament or cathode circuit, or both, the employment of devices to smooth out fluctuations of current so derived'from light and power circuits has been found to be necessary, particularly where the light and power circuit carries alternating current which must first be rectified before the admission of such current to a radio receiving set can Abe permitted. Such filtering devices, however, generally work at alternations or fiuctuations of current of low frequency and present no obstacle -to the transmission of the impulses of very high or radio frequency which may be picked up on the supply lines and be transmitted to the radio set, in which l they seriously interfere with the regular riol mode of operation. For such low frequency filter devices to work properly, all radio frequency impulses which may be picked up by the supply lines and travel along the latter `quency oscillations or fiuctuations and pre- 1926. Serial No. 109,500.

to the radio frequency set must be removed; and my invention is designed particularly to serve this pur ose. It comprises an additional filter capa le of suppressing radio fre- 55 vent them from reaching the radio set, so that the latter is energized' by the modified current of the supply line and nothing more. In practice a radio frequency filter according to y invention may be disposed between the low frequency supply line filter and vthe receiving set, and is connected to the output of the low frequency filtering device. Thus, radio frequency impulses which may travel by way of the 'supply line through a low frequency filtering device without being changed, are eliminated whentheradio frequency filteris reached; but the current derived from they light o r power cir-l cuit and \modifled; by the low frequency filtering device can fiow through the radio frequency filter of my invention without loss or hindrance, and thus the desired end-is attained.

Figure 1 shows one form of suchl a radio 7l frequency filter having input terminals 1 and 2 to be united to the output terminals of the low frequency filter; and this radio4 frequency filter comprises a pair of conductors or leads L, havingV output terminals 3 and 80 4 to-which conductors leading to the radio receiving set can be united. OneV of the conductors L has a coil 5 with an iron core in series with a radio frequency choke coil 6. The other lead L has a similar radio frequency choke coil 7 and across the two terminals of the coils 6 and 7 I may bridge condensers 8 and 9. A steady current can pass through the coils 5, 6 and 7 without obstruction, but anyradio frequency impulses reaching the coils 6 and 7 will be suppressed entirely, or caused to fiow continuously in the'local circuit made up of the two coils 6 land 7 and the two condensers 8 and 9, and none of this vradio frequency current will flow` out of the filtering device past the output terminals 3 and 4 to the radio receiving set to which these terminals are attached.

In Figure 2 a similar arrangement is 00 shown, except that the coil 7 is omitted and in place of the condenser 8 I employ two condensers 8' having a common terminal united to ground by conductor 10. All impulses of radio frequency are obviated by this circuit by being conducted away to earth.

Figure 3 shows a third form in which the arrangement is the same as that of Figure 1 with the coil 7 omitted, the radio frequency impulses here being suppressed by the coil 6 andthe two condensers 8 and 9.

The radio frequency filter above described may, of course be used by connecting it first to the supply line and having the low freuency supply line filter between the radio requency filter and the receiving set; as 4well as by putting the radio frequency filter between the set and the` low frequency supply line lter in the manner above sety forth.

Having described my invention, what I believe to be new and desire to secure and protect by Letters Patent of the United States is 1. An interference eliminator for connec# tion between radio receiving apparatus and a source of power supply, comprising a series connected choke coil for suppressing low freuency disturbances, a series connected high equency choke coil, and condenser connectedin circuit with the high frequency choke to form an oscillatory circuit for preventing the passing of radio frequency disturbances.

2. An interference eliminator for connection between radio receiving apparatus and a source 'of power supply, comprising a. choke coil for suppressing low frequency disturbances, a radio frequency choke coil in series with the low frequency choke, and a plurality of condensers connected in multiple with the radio frequency choke to form an oscillatory circuit for preventing the passing of radio frequency disturbances.

3. An interference eliminator for connection vbetween radio receiving apparatus and a source of power supply, comprising a choke coil for preventing the passing of low frequency disturbances, a radiofrequcncy choke coil connected in series with the low frequency choke, condensers connected across said radio frequency choke to form an oscillatory circuit therewith for preventing 'the passing of radio frequency disturbances, and means for capacitively connecting each side of the eliminator circuit to ground to drain olf disturbances.

In testimony whereof I aiix my signature.

HARRY w. HoUoK. 

